The present invention relates to a system for measuring stress in an object.
A portion of the disclosure of this patent document contains material to which is subject to a claim of copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all other rights whatsoever.
Various non-destructive techniques have been proposed to measure and analyze stresses in a physical object. For example, U.S. Pat. No. 4,378,701 discloses a technique whereby stress is analyzed by detecting thermal radiation produced by a part subject to stress. This technique is utilized in a computer controlled stress analyzing system (SPATE 8000) marketed by Ometron, Inc.. This known system detects the minute temperature changes which arise when an object is cyclically loaded. These temperature changes are correlated with a reference signal which represents the applied load. However, this known system may produce inaccurate results due to overload conditions caused by intermittent thermal disturbances or caused by a strong source of thermal radiation source moving into the field of view of the scanning infra-red detector.
If an operator is not present during occurrence of the overload condition, then the known system will retain faulty data caused by the overload. If an operator is present and recognizes an overload situation, the operator can manually adjust the sensitivity to eliminate the overload condition. However, the system will then have acquired two sets of data obtained under different conditions, thus preventing the uniform displaying of such data.